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最近在学习langchain4j，本文将介绍如何使用langchain4j快速实现一个简单的问答功能，帮助大家快速入门。

1. 工具

• JDK 17
• Maven 3.9.9
• IntelliJ IDEA 2024.3.4 (Community Edition)

2. apikey

可以优先选择阿里云百炼申请一个apikey，免费额度足够测试使用。

3. springboot项目创建

3.1 项目创建

创建springboot项目，与其他springboot项目创建方式一样，这里不再详细介绍。

3.2 依赖引入

这里只提供了部分依赖示例，使用的版本是1.0.0-beta2，完整依赖可以参考langchain4j官方文档，本文最后给出了完整pom.xml供大家参考。实际上三方依赖会经常更新，随着版本变化需要引入的依赖总是会有些区别，还是建议多查阅官方文档。

<!-- springboot 父依赖 -->
<parent><groupId>org.springframework.boot</groupId><artifactId>spring-boot-starter-parent</artifactId><version>3.4.4</version>
</parent><dependencies><!-- springboot web 模块 --><dependency><groupId>org.springframework.boot</groupId><artifactId>spring-boot-starter-web</artifactId></dependency><!-- langchain4j 集成 springboot相关的依赖 --><dependency><groupId>dev.langchain4j</groupId><artifactId>langchain4j-open-ai-spring-boot-starter</artifactId></dependency><dependency><groupId>dev.langchain4j</groupId><artifactId>langchain4j-spring-boot-starter</artifactId></dependency><dependency><groupId>dev.langchain4j</groupId><artifactId>langchain4j-open-ai</artifactId></dependency><dependency><groupId>dev.langchain4j</groupId><artifactId>langchain4j</artifactId></dependency>
</dependencies>

3.3 配置文件

application.yml 配置文件内容如下：

langchain4j:open-ai:chat-model:log-requests: truelog-responses: truetemperature: 0.5max-tokens: 4096base-url: https://dashscope.aliyuncs.com/compatible-mode/v1model-name: qwen-plusapi-key: ${API_KEY} # 需要替换成自己申请的apikey# base-url: https://api.deepseek.com/v1# model-name: deepseek-reasoner# api-key: ${API_KEY}logging.level.dev.langchain4j: DEBUG

4. 代码编写

4.1 启动类

先准备springboot启动类

import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;@SpringBootApplication
public class Application {public static void main(String[] args) {SpringApplication.run(Application.class, args);}}

4.2 controller

编写一个接口，注入ChatLanguageModel，写一个最简单的接口测试。

import dev.langchain4j.model.chat.ChatLanguageModel;
import dev.langchain4j.service.AiServices;
import jakarta.annotation.Resource;
import org.springframework.web.bind.annotation.GetMapping;
import org.springframework.web.bind.annotation.RequestParam;
import org.springframework.web.bind.annotation.RestController;@RestController
public class ChatController {@ResourceChatLanguageModel chatLanguageModel;@GetMapping("/chat")public String model(@RequestParam(value = "message") String message) {return chatLanguageModel.chat(message);}
}

4.3 测试

启动项目，用postman调用接口进行简单测试：

参考

完整的pom.xml文件如下

<?xml version="1.0" encoding="UTF-8"?>
<project xmlns="http://maven.apache.org/POM/4.0.0"xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd"><modelVersion>4.0.0</modelVersion><groupId>cn.chenf24k.tools</groupId><artifactId>cf-langchain</artifactId><version>1.0-SNAPSHOT</version><parent><groupId>org.springframework.boot</groupId><artifactId>spring-boot-starter-parent</artifactId><version>3.4.4</version></parent><properties><maven.compiler.source>17</maven.compiler.source><maven.compiler.target>17</maven.compiler.target><project.build.sourceEncoding>UTF-8</project.build.sourceEncoding><langchain4j.version>1.0.0-beta2</langchain4j.version></properties><dependencyManagement><dependencies><dependency><groupId>dev.langchain4j</groupId><artifactId>langchain4j-bom</artifactId><version>${langchain4j.version}</version><type>pom</type><scope>import</scope></dependency></dependencies></dependencyManagement><dependencies><dependency><groupId>org.springframework.boot</groupId><artifactId>spring-boot-starter-web</artifactId></dependency><dependency><groupId>dev.langchain4j</groupId><artifactId>langchain4j-open-ai-spring-boot-starter</artifactId></dependency><dependency><groupId>dev.langchain4j</groupId><artifactId>langchain4j-spring-boot-starter</artifactId></dependency><dependency><groupId>dev.langchain4j</groupId><artifactId>langchain4j-open-ai</artifactId></dependency><dependency><groupId>dev.langchain4j</groupId><artifactId>langchain4j</artifactId></dependency><dependency><groupId>org.mapdb</groupId><artifactId>mapdb</artifactId><version>3.0.9</version><exclusions><exclusion><groupId>org.jetbrains.kotlin</groupId><artifactId>kotlin-stdlib</artifactId></exclusion></exclusions></dependency></dependencies><build><finalName>app</finalName><plugins><plugin><groupId>org.springframework.boot</groupId><artifactId>spring-boot-maven-plugin</artifactId></plugin></plugins></build></project>